Internal-combustion percussion tool



May 8, 1951 c. s. wEYANDT INTERNAL-COMBUSTION PERCUSSION TOOL.

Original Filed July so, 194:5

Inventor. el 5. ln/EyA/var att orneg Patented May 8, 19951 INTERNAL-COMBUSTION PERCUSSION TOOL Carl S. Weyandt, Homer City, Pa.

Original application July 30, 1943, Serial No.

496,709, now Patent No. 2,433,007, dated Deccmber 23, 1947.

Divided and this application July 18, 1947, Serial N0. 761,826

6 Claims. l

'I'he present invention relates to percussion tools operated by internal combustion of a fuel, and relates particularly to such tools employing a free working piston.

This invention is a division of application Serial No. 496,709, filed July 30, 1943, now Patent 2,433,007, issued December 23, 1947, for Internal Combustion Percussion Tool.

Heretofore it has been proposed to provide a percussion tool of this type having a captive piston which controls the combustion of the fuel and a free differential piston which is impacted against the tool by the combustion of the fuel and is returned by the pressure of the exhaust gases, the return stroke being cushioned by a gas cushion. However, I have found that in operation the reciprocation of the differential or working piston is irregular so that the blows delivered thereby are not uniform, nor is the maximum power of the apparatus developed.

It is an object of this invention to improve the operation of percussion tools of this type to provide a more uniform operation of the working piston.

Another object is to increase the efficiency of the apparatus by increasing the power of the working piston.

Another object of this invention is to provide a device of this kind in which the action of the working piston may be controlled independently of the idling piston.

According to one feature of the present invention, I provide an internal combustion percussion tool having an idling piston and a differential working piston driven in one direction by combustion of the fuel and returned by the pressure of exhaust gas, the admission of exhaust gas to return the differential working piston being controlled by a valve actuated by the crankshaft of the internal combustion percussion tool.

For a detailed description of the invention, reference is had to the following specification taken in connection with the accompanying drawing, wherein preferred embodiments of the invention are shown by way of example, vand wherein:

Fig. 1 is a view partly in vertical section and with parts broken away of the internal combustion percussion tool comprising this invention.

Fig. 2 is a side view in elevation of the valve operating mechanism shown in Fig. l with parts broken away.

Referring to the drawing, Fig. 1, there is shown a casting or motor block I of cast iron having heat radiating ns and having a bore 2Y therein which provides a chamber or cylinder in which the piston 3, which is called an idling piston, is adapted to reciprocate. This piston is suitably connected, as by a connecting rod 4, with the crankshaft 5 journaled in suitable ball bearings in the crankcase 6 bolted to the housing I. The lower part of the housing accommodates a working piston 9 to be later described in detail, and the middle part I of the housing serves as a combustion chamber.

Gasoline, containing oil for lubrication of the moving parts of the apparatus, is contained in a tank, not shown, suitably attached to the apparatus, and is mixed with air in a carburetor of suitable construction. On the down stroke of piston 3 a mixture of air and gasoline is drawn into the piston chamber 2 through the divided intake port I2 which is uncovered by the piston skirt near the lower end of its stroke, and when the piston moves upwardly it compresses the fuel charge in the crankcase 6. As the piston continuesto move upwardly it first uncovers the exhaust port I5 and then uncovers the intake port I4, thus forcing the combustible charge from the crankcase through the conduit IS and port I4 into the combustion chamber l, the piston head being suitably balfled to prevent the incoming fuel being discharged through the exhaust port. The crank returns the piston to Acompress the charge in combustion chamber l,

which is ignited by the spark plug I3, the electric current for operating the spark plug being obtained from a combination magneto and flywheel on the crank shaft 5. An external line 20c is connected to the exhaust port I5 to deect the exhaust downward.

The bore 2| inthe casing below the combustion chamber constitutes a prolongation of bore 2 and receives the smaller end 22 of the hollow steel working piston 9, which is hardened and has a highly polished working surface, and a counterbore '24 in the casing receives the enlarged portion 26 of the piston -9 which divides counterbore 24 into chambers 24a and 24h. The enlarged portion 26 preferably has twice the area of end 22 which may be of any size desired, and need not be, but preferably is, the same diameter as piston 3. Suitable rings and an oil groove may be provided to form a sealing contact between the piston 9 and the walls of chambers 2| and 24. I prefer to provide a working clearance between the piston and its chamber of about 0.005 inch to prevent seizing at the elevated temperature created in operation. Piston 9 has an extension 28 which passes with a close t through a guide bushing l29 of tool steel or other suitable material and is adapted to strike the end of a tool of any kind, such as a drill or tamper bar, loosely received in the tool holder 32 and longitudinally movable therein. Guide lbushing 29 is clamped between the block l and the anged tool holder or sleeve 32 in any suitable manner, and a -dowel may be provided for proper positioning thereof. The working piston 9 preferably is guided in its reciprocation by the stem or extension 28 working in guide bushing 29 and the smaller end 22 working in bore 2|, and the enlarged portion 26 need not have an vaccurately controlled clearance with the cylinder wall 24 as it carries a sealing ring of known construction which extends beyond the surface thereof and contacts the bore.

The guide bushing 29 is recessed at 39 to co-` operate with a slot 3l and two slots 38 located in the end of member 28 which allows the escape of gas therefrom to the atmosphere. Slot 131 is of such length that when the working piston is at the upper limit of its stroke its upper end is uncovered by the recess 3S so that slot 31 and both slots 38 in this position register with the bottom of recess 36 and thus provides Va relatively free escape for gas from the chamber 24h to atmosphere. On the downward stroke slot 3T first moves out of registry with depression .36 thus lcutting down the rate of escape of gas from chamber 24h and then slots 38 move out of register so that all slots are disconnected from chamber 24h when the extension 2-8 impacts the tool. Should the tool be raised from the work during operation there is thus provided a gas cushion trapped in the lower end of lchamber Zlib to prevent the piston impacting the housing.

The lower portion 65 of the casing for housing the working piston is separate from the upper part I and is suitably secured thereto to enable drilling the various passages required. A valve block 5B has a threaded boss 6l threaded into a bore 68 in the lower casing l65 and passage 58 communicates with a passage 69 therein. The valve block has threaded bores 'Il and l2 at its ends and a connecting portion or chamber 13 to provide a valve seat 1A.

The working piston 9 is made hollow and is closed at its upper end by a plug 22a threaded against a shoulder 22h and welded at 22e. In the valve block 66 a valve 15 of the poppet type is seated on the seat 'i4 and has a stem 16 extending through the bushing 11, the opposite vbore 'l2 being closed by a cap screw 18. An L-shaped passage 19 in the threaded boss 61 leads to annular groove 89 and connects chamber I3 with the longitudinal passage 8| which connects by port 82 with the lower portion 24h of chamber 24. A threaded plug 83 closes the end of passage Bl and may be removed to allow the cleaning of the passage.

A bracket 85 extends from adjacent the upper end of the motor block l and carries a guide bushing 89 through which extends the valve stem 16 terminating in an adjustable head -8'1 held in place by a lock nut 98. A tappet 89 is pivoted at 9| to the bracket 85 and is interposed between cam 92 secured on crankshaft v5 and head 8l. Cam 92 has a depressed portion '93 and an elevated portion 94. A spring 95 abuts a collar 96 held on the lower portion of the valve stem 'I9 by a retainer 91, the lower end of the spring abutting the bushing 1l.

An annular buffer '98 is secured at the upper end of chamber 24a in any suitable manner as by countersunk screws 98 and a passage 35 allows free entrance and escape of air from this chamber.

In operation passage 58 is closed from passage 82 by Valve 'I5 held closed by spring 95 and the pressure of gas on the valve, and when an explosion in chamber l occurs the working piston 9 Iis driven downward tol bring extension 28 into forcible contact with the tool 3|, the grooves 3l and 3.8 allowing escape of air or gas from chamber r21lb at the initial part of this movement, all as previously described. At the same time, captive piston 3 is driven upward to rotate the :crankshaft 5, which rotates cam 92. Cam 92 is positioned so that shortly after the explosion the elevated portion 9G contacts head 91 through tappet 89 to depress the valve stem i6 and hold valve 'i5 open, thus allowing exhaust gas to enter chamber Zlib and force piston 9 upward. Valve T5 may be kept open until just prior to the next explosion, when it is closed by the spring 95 and depressed portion 93 of the cam 92 on crankshift 5, or by adjusting the head 81, or by doing both, to cause the valve to open at the proper time, and to close at the proper time. In this way a smooth, uniform operation of the working piston may be obtained.

I claim:

1. In an internal combustion percussion tool, the combination of a combustion chamber, a crankshaft mounted thereon, a timing piston reciprocable in the combustion chamber and operating the crankshaft to control the combustion of fuel in the combustion chamber, a tool-actuating free working piston having one end recipro.

cable in said combustion chamber, a second chamber for receiving the other end of the free working piston, the combustion of fuel in the combustion chamber operating the working piston onf its power stroke, a passage one end of which is open at all times to the combustion chamber between said pistons and connected to said second chamber beyond the end of the working piston, and an adjust-ably timed valve intermediate the ends of said passage and operated by the .crankshaft to control the admission of gas through the passage for returning the Working piston.

2. A percussion tool comprising a combustion chamber, an idling piston reciprocable in said chamber, a second larger chamber connected therewith, a free differential area working piston having one end operating in said combustion chamber and having the other larger end operating in said larger chamber, a passage one end of which is open at all times to said combustion chamber between said pistons and connected into said larger chamber beyond the larger end` of the piston, and a valve intermediate the ends of said passage and the timing of which is adjustable relative to and is operated by the idling piston to control the admission of gas from the combustion chamber to the larger chamber.

3. In an internal combustion percussion tool, the combination of a housing capable of being manipulated, a rotary crankshaft carried yby the housing, a combustion chamber in the housing,l

a timing piston reciprocable in the combustion chamber and connected to rotate the crankshaft,`

a second larger chamber connected with the combustion chamber, a free differential area working piston having its smaller end operating in the combustion chamber and its larger end opening in the larger chamber, a passage one end of which is open at all times to thel combuB- tion chamber between said pistons and connected with the larger chamber beyond the end of the working piston, and a Valve intermediate the ends of said passage and the timing of which is adjustable relative to and is operated by the crankshaft and arranged to control the admission of gas through the passage from the combuston chamber to the larger chamber for returning the working piston.

4. In an internal combustion percussion tool, the combination of a housing, a rotary crankshaft carried by the housing, a combustion chamber in the housing, a timing piston reciprocable in said combustion chamber and connected to rotate said crankshaft to control the combustion of fuel therein, a tool-actuating working piston having one end reciprocable in said com-- bustion chamber and operated by the combustion of fuel therein, a second chamber for receiving the other end of the free working piston, a passage one end of which is open at all times to the combustion chamber between said pistons and connected to the second chamber beyond the end of the working piston, and a Valve intermediate the ends of said passage and operated by the crankshaft to control the timing of the admission of gas from the combustion chamber to said second chamber to return the working piston.

5. In an internal combustion percussion hand tool, the combination of a housing, a rotary crankshaft carried by the housing, a differential cylinder in the housing, a timing piston connected to the crankshaft and operating in the small end of said cylinder and functioning to control the combustion of fuel therein, a tool-actuating differential Working piston reciprocable in said chamber in opposition to the timing piston and operated by the combustion of fuel, a passage oneV of gas to return the working piston after each working stroke, and resilient means adjacent the juncture of the differential cylinders for cushioning the working piston on its return stroke.

6. In an internal combustion percussion hand tool, the combination of a housing, a rotary crankshaft carried by the housing, a differential cylinder in the housing, a timing piston connected to the crankshaft and operating in the small end of said cylinder and functioning to control the combustion of fuel therein, a tool-actuating differential working piston reciprocable in said chamber in opposition to the timing piston and operated by the combustion of fuel, a passage one end of which is open at al1 times to the combustion chamber from between the pistons to beyond the larger end of the Working piston, a valve intermediate the ends of said passage and operated by the crankshaft to control the admission of gasI to return the Working piston after each working stroke, resilient means adjacent the junction of the differential cylinders for cushioning the working piston on its return stroke, and slot means on the working piston to exhaust the gas from beyond the larger end of the working piston as it approaches the end of its return stroke.

CARL S. WEYANDT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,837,947 Bunn Dec. 22, 1931 1,920,765 Rasch Aug. 1, 1933 1,981,764 Warsop Nov. 20, 1934 FOREIGN PATENTS Number Country Date 54,176 Norway July 16, 1934 

